Substrate processing may include deposition and etch processes on a substrate. Deposition processes may include chemical vapor deposition (CVD) and atomic layer deposition (ALD). Chemical vapor deposition (CVD) is a process used to deposit thin films for semiconductor fabrication. CVD typically includes introducing one or more reagents (e.g., precursors) to a substrate in a processing chamber. The reagents react and/or decompose to deposit the films. Longer CVD processing times (i.e., longer exposure to reagents) increase layer thickness. Plasma enhanced CVD (PECVD) uses plasma in the processing chamber to increase the reaction rates of the reagents and may allow deposition at lower temperatures. Plasma species can also be used to modify resulting film properties.
Atomic layer deposition (ALD) is a process used to deposit conformal layers with atomic scale thickness control during various semiconductor processing operations. ALD may be used to deposit barrier layers, adhesion layers, seed layers, dielectric layers, conductive layers, and the like. ALD is a multi-step self-limiting process that includes the use of at least two reagents. Generally, a first reagent (which may be referred to as a precursor) is introduced into a processing chamber containing a substrate and adsorbs on the surface of the substrate. Excess precursor is purged and/or pumped away. A second reagent (e.g., water vapor, ozone, or plasma) is then introduced into the chamber and reacts with the adsorbed layer to form a deposited layer via a deposition reaction. The deposition reaction is self-limiting in that the reaction terminates once the initially adsorbed layer is fully reacted with the second reagent. Excess second reagent is then purged and/or pumped away. The aforementioned steps constitute one deposition or ALD “cycle.” The process is repeated to form the next layer, with the number of cycles determining the total deposited film thickness. Plasma enhanced ALD (PEALD) is a variant of ALD that uses plasma as the second reagent, where plasma constitutes a quasi-static equilibrium of ions, radicals and neutrals derived from the constituent feed gasses.
CVD and ALD can be performed using a processing chamber that includes a showerhead disposed above a substrate. Reagents may be introduced to the substrate through the showerhead. For plasma enhanced processes, plasma can be generated using a radio frequency (RF) or direct current (DC) discharge between two conductive surfaces (e.g. electrodes) in the chamber. The discharge is used to ignite reacting gasses in the chamber.
Etching can also be performed using a processing chamber that includes a showerhead disposed above a substrate. Reagents, including etch gases, may be introduced to the substrate through the showerhead. For plasma enhanced processes, plasma gas may be introduced into the chamber and reacts with the etch gases to pre-treat or etch one or more materials on a substrate. Plasma can be generated using a radio frequency (RF) or direct current (DC) discharge between two conductive surfaces (e.g. electrodes) in the chamber.
Semiconductor research and development is typically performed by using production tools. Therefore, to explore new CVD and ALD techniques or to evaluate materials deposited using CVD or ALD, a layer is deposited over an entire wafer. Similarly, to explore new etch techniques, an entire substrate is grounded and plasma energy is focused on an entire wafer. The process of investigating semiconductor processes and materials in this way can be slow and expensive.